Fully Associative Mapping

The most conceptually simple scheme for mapping RAM blocks to cache block frames is called fully associative mapping. Under this scheme, any RAM block can be stored in any available block frame. Fully associative mapping is depicted in Figure 11-6, where any of the red RAM blocks can go into any of the red cache block frames.

The problem with fully associative mapping is that if you want to retrieve a specific block from the cache, you have to check the tag of every single block frame in the entire cache because the desired block could be in any of the frames. Since large caches can have thousands of block frames, this tag searching can add considerable delay (latency) to a fetch. Furthermore, the larger the cache, the ...

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